The use of computer or communications networks, including Local Area Networks (LANs), Wide-Area Networks (WANs), and the Internet continues to grow at ever increasing rates. Each day, more and more computer systems or communications devices are becoming interconnected in such wired or wireless networks, which typically communicate data in packets. This has created a need for high performance network switches, such as for use by network service providers. Many such switches comprise multiple modules, with many data flows between the modules themselves and between the interfaces to external networks. A data flow is sometimes called an “IP flow,” which refers to a stream of packets that enter and exit the same set of interfaces. The packets of a particular IP flow have the same values in the IP packet header for the following six attributes of the IP packet header: (1) Source IP Address, (2) Source L4 Port, (3) Type of Service (TOS), (4) Destination IP Address, (5) Destination L4 Port, and (6) Protocol.
In some cases, the network switch modules, including the processors residing in the modules, can be partitioned into virtual routers (VRs), that is, software running on the processors that emulates the functioning of an individual physical hardware router. As a result of the combination of hundreds of thousands of data flows for the virtual routers in these network switches, there is a need for efficiently processing packet data flows, and for controlling the resources consumed within the network switch.
As broadband network access becomes more available, individual subscribers of network service providers have more available options for different services and service levels. Even the same subscriber may have different service needs at different times. As an illustrative example, a first subscriber may desire high definition television (HDTV) service over a network. A second subscriber may desire mobile telephone service over the network. The first subscriber may occasionally desire video-on-demand (VOD). The second subscriber may need to switch between voice communication and high-speed digital data communication.
A “unicast” communication typically refers to a communication from a single source device to a single destination device over a network. By contrast, a “multicast” communication typically refers to a communication to a group of destination devices from one or more source devices. Multicast packet forwarding raises additional complexity because of the many destination devices. Many existing router devices will be unable to provide the desired scalability to accommodate such additional destination devices. This is particularly true when each individual data flow may require “per-flow” services for the multicast traffic. Allocating resources efficiently for a large number of multicast data flows is a challenging problem. Moreover, multicast broadcasting of content presents additional complexity because individual users may join or leave a particular multicast group at will and often. Such “channel surfing” creates an additional burden for keeping track of the participants of a multicast group so that the content can be routed appropriately.